.wel_box{
  width: 100%;
  height: 100vh;
  line-height: 0;
  position: relative;
}
.back_img{
  width: 100%;
  height: 100%;
  display: block;
}
.login_butt{
  width: 250rpx;
height: 100rpx;
position: absolute;
bottom: 100rpx;
left: calc((100% - 250rpx) / 2);
line-height: 100rpx;
font-size: 28rpx;
padding: 0;
border: 2rpx solid #fff;
color: #fff;
background: #0AC2AE;
}